Construction worker Ti (Stephen Chow) lives in a ramshackle shanty and scavenges everything from shoes to toys from the trash dump. Despite his state of abject poverty, the earnest, lesson-spouting Ti is determined to send his son Dicky (Xu Jiao) to a posh private elementary school. Dicky, however, is a lot more interested in playing than studying, and he'd like nothing more than a CJ1 robot dog to show up his bullying classmate. Unable to afford a CJ1, Ti brings home "CJ7", a curious rubbery green ball he found at the dump. His son isn't impressed - until the ball shows its true alien form, morphing into a little green dog whose penchant for mischief gives even Dicky a run for his money.

Stephen Chow has helped launched the careers of many a starlet, and this time CJ7 co-stars Mainland newcomer Kitty Zhang and talented child actress Xu Jiao who genderbends as Chow's son. Chow was so impressed with Xu Jiao's performance, he not only has more plans in store for the budding ingenue, he's adopted her as his goddaughter. Other key comedy players include portly Stephen Chow regular Lam Chi Chung and the cuddly titular alien that serves as another testament to Chow's ability to effectively integrate state-of-the-art CGI into his films.